Have a corrupted file in InDesign C5.5, please help
The first problem, and maybe all of it, is that CS5.5 is really, really obsolete even if it's running on an original OS and platform. Many things have changed outside the software itself and it may simply not run any more without glitches.
That said, there's a fairly universal fix for file corruption in InDesign. Save the file (or export it — it varies with the specific software revision) to IDML format, then reopen it as an INDD file.
I can't say for sure where this option might be. In current versions, you can both "Save As" IDML and "Export" to the format. CS5.5 might have either or both.
And the other fix is to always save archive copies of work, after each major addition or change if not daily. Doing a lot of work with only one file that can get damaged or deleted is walking a tightrope. Save, save, save to a continuing series of back up copies.
It's very unlikely. If the file is so corrupted ID won't open it, I am not sure there's any good process for getting the content out again.
It couldn't hurt to try and open it with any later version, as it could be an app/OS/system fault rather than something with the file. Maybe a trial version of ID is worth downloading.
Perhaps someone with very specific experience at recovering bad files has a better answer, but I'm pretty sure the past consensus has been "it's gone." Sorry...
I'd be willing to take a stab at it if you want to share the file here.